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I've read on Wikipedia about Space Weathering. It's described as the type of weathering that occurs to any object exposed to the harsh environment of outer space. Unlike on Earth, a man-made vessel wouldn't be affected by rain or wind. But the constant flux of high energy particles and micrometeorites.

If I've understood the article, it appears that over time Space Weather would darken man-made materials. But the article describes melting and vapor as well.

What would this look like over time? I assume painted surfaces would show the same weathering. Are there any examples of man-made devices where we've actually seen space weathering?

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    $\begingroup$ It's pretty hard to decide which answer get's the green check mark. Both are really good answers. $\endgroup$ – Maelish Nov 11 '18 at 14:34
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There are four(ish) primary contributors to "space weathering" of any material (natural or synthetic) in space:

  1. Micrometeoroid and debris environment: This is the result of small stuff hitting the material in question. At possible collision speeds of up to 14 km/s (for debris, much higher for micrometeoroids) everything becomes a bullet. The classic example is the pitted space shuttle window. Of course, a larger impact will lead to the ultimate "weathering"
  2. Outgassing: Also known as the "new car smell". Any object in a vacuum, will tend to outgas any volatiles. Your car outgases from some of its materials/binders/adhesives leadingto the distinctive smell. This is one of the reasons certain materials are frowned upon in spacecraft. Some plastics/foams will outgas themselves to nothingness. Others will just become brittle or crumbly. In addition to potentially damaging the outgassing material due to mass loss, outgassed particles tend to deposit themselves in nearby cold surfaces - such as lenses and solar cell cover glasses.

    As a result, materials used in spacecraft design are chosen with minimal outgassing as a significant criteria. One material which you'll often hear spacecraft engineers talk about is Kapton tape - the duct tape of rocket scientists. Kapton is particularly stable in a vacuum (among other properties), and, therefore, is extensively used.

  3. Atomic Oxygen: In the upper reaches of the atmosphere, roughly between 150 to 700 km, oxygen molecules (O2) disassociate into individual oxygen atoms (O). These atoms are highly reactive and like to bind (oxidize) to many other substances. This can result in erosion of of surfaces, darkening of optics, etc.
  4. Radiation (EM and particle): Radiation of all sorts can also affect materials. Polymers are again especially susceptible. the results can vary between changing optical properties (darkening, for instance) to structural changes. UV light, for instance, can slowly deteriorate plastics. Ever seen a car seat where the exposure to sunlight ultimately made the vinyl all crumbly and yucky? Some CubeSats have actually taking advantage of this. The antennas are held down in place before deployment by fishing line. Normally, the fishing line is melted to allow the antennas to deploy. If the melting, doesn't work, a backup is to wait until the UV light deteriorates the fishing line to the point where it breaks.

Not surprisingly, NASA has carried out lots of experiments to study the effects of the space environment on materials. One of the earliest was the Pegasus program - where very large panels deployed form the service module (SM) stand-in of test Saturn I rockets. The panels were instrumented (with effectively a microphone) that counted impacts of micrometeoroids. Years later, NASA flew the Long Duration Exposure Facility (LDEF), a bus-sized satellite completely enveloped in exterior panels with different materials to be tested.

More recently, NASA has flown several Materials Integration Space Station Experiment (MISSE) payloads to the space station. You can see the effects of Atomic Oxygen on the MISSE-2 mission in this incredible picture:

Materials Integration Space Station Experiment-2 before and after 4 years of space exposure.

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    $\begingroup$ Excellent post! One small nit: the meteoroid environment includes impacts at velocities up to 70 km/s. 15 km/s pretty well envelopes the overwhelming majority of the debris environment, but meteoroids are a great deal faster. $\endgroup$ – Tristan Sep 28 '18 at 16:37
  • $\begingroup$ @Tristan - Agreed on impact velocities. I was thinking of debris impact (7km/s * 2) I will edit. $\endgroup$ – Carlos N Sep 28 '18 at 20:04
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The Long Duration Exposure Facility (LDEF) was a Shuttle-launched and -retrieved satellite designed to investigate exactly this.

Here is the LDEF in space.

enter image description here

It was covered in trays of different materials to investigate how they stood up in low Earth orbit.

It was supposed to stay in orbit about a year, but the Challenger failure intervened, causing it to stay up for ~ 6 years.

Source

There was a conference called "LDEF Materials Results for Spacecraft Applications" in 1993, the proceedings are available online and are a gold mine of information about the results of the experiments.

Conference proceedings

Here's one example from the paper showing how atomic oxygen eroded Kapton multi-layer insulation.

enter image description here

This picture is from the LDEF retrieval mission, you can see some of the effects (peeling layers at the bottom end of the satellite, etc).

enter image description here

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    $\begingroup$ Wow. Look at the difference on the scuff plate for the sill trunnion pin! Yellow at deployment, chocolate brown at retrieval. And nearly everything near it also turned brown. $\endgroup$ – Tristan Sep 28 '18 at 16:41
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    $\begingroup$ @Tristan I was going to mention that but I wasn't sure if lighting might be a contributor. My gut feel is that it's real though. $\endgroup$ – Organic Marble Sep 28 '18 at 17:19
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    $\begingroup$ @Tristan Just a guess, it was cadmium yellow (CdS) paint, and in the atomic oxygen environment, it oxidized into CdO, which is brown. $\endgroup$ – user71659 Sep 29 '18 at 5:32

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